Frame of motorcycle and engine bracket

ABSTRACT

A frame of a motorcycle includes a head pipe configured to support a steering shaft, a first frame configured to extend from the head pipe, through above and rearward of an engine, and to rearward of a vehicle body, a second frame that is located under the first frame and configured to extend from the head pipe, through forward and downward of the engine, and to rearward of the vehicle body, a bracket by which a first component is mounted to the second frame, and a coupling member that is mounted to the second frame to couple a second component to the second frame, and the bracket is integral with the coupling member. An engine bracket of a motorcycle is manufactured by forging such that a region subjected to tensile stress is made thicker than a region in the vicinity of the region which is subjected to the tensile stress.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 11/315,584, entitled FRAME OF MOTORCYCLE AND ENGINEBRACKET, filed Dec. 21, 2005. The entire disclosure of this applicationis hereby incorporated by reference.

TECHNICAL FIELD

The present invention generally relates to a frame of a motorcycle, andan engine bracket by which an engine is mounted to the frame.

BACKGROUND ART

Some frames of motorcycles include a head pipe that supports a steeringshaft with a steering handle attached to an upper portion thereof, amain frame extending rearward from the head pipe, a down tube extendingdownward from the head pipe, a lower frame extending substantiallyrearward from a lower end portion of the down tube, and a pivot frame(also referred to as a swing arm bracket) extending downward from a rearend portion of the main frame, by which a rear end portion of the lowerframe is coupled to the rear end portion of the main frame. Such aconstruction is disclosed in Japanese Laid-Open Patent ApplicationPublication Nos. 2004-331001 and 2004-330999.

Various components are incorporated into the frame including the mainframe, the pivot frame, the down tube, and the lower frame. Oneexemplary component is an engine mounted in the frame by a plurality ofbrackets. In the case of a water-cooled engine, a radiator is disposedin front of the down tube and is mounted on the down tube by brackets.Especially in motocross motorcycles, an engine guard is disposed tocover an engine from below and is mounted on the lower frame bybrackets. In order to enable the main frame and the down tube to befirmly coupled to the head pipe, the main frame and the down tube aresometimes coupled to each other by reinforcing gussets.

Typically, the brackets and the gussets are manufactured separately andwelded to the frame. In this case, it is necessary to weld the bracketsand other components to the frame so that the components, for example,the engine, the radiator and the gussets, are incorporated into theframe with positioning accuracy. The process for welding a number ofcomponents is complicated, making it difficult to improve productivity.

Other frames of motorcycles include right and left main frames extendingrearward from a head pipe, right and left pivot frames extendingdownward from rear end portions of the main frames, and a cross membercoupling the right and left pivot frames to each other. A swing arm forrotatably supporting a rear wheel at a rear end thereof is verticallypivotally mounted at a front end portion thereof to one of the right andleft pivot frames, and a suspension unit such as a shock absorber isdisposed between the swing arm and the cross member and is mounted tothe cross member by brackets mounted on the cross member.

In a frame thus constructed, a large load is applied to the main frames,the pivot frames, and the cross member. Since the engine, which has alarge weight, is supported by the main frames and the pivot frames viathe brackets, the load of the engine is applied to the respectiveframes. During travel of the motorcycle, a rider and the motorcycle aresupported by a front suspension unit mounted to a front fork extendingdownward from the steering shaft and a rear suspension unit mountedbetween the swing arm and the cross member, a large load is applied tothe cross member on which the rear suspension unit is mounted.Therefore, it is desirable to firmly couple the main frames, the pivotframes, and the cross member to each other.

Exemplary brackets by which the engine is coupled to the frames aredisclosed in Japanese Published Examined Application No. Hei. 7-71953.The brackets are constructed of flat plates.

Since the engine has a large weight as described above, the brackets bywhich the engine is coupled to the frame are required to have strength.In order to allow the rider to easily manipulate a vehicle body duringcornering, the brackets are required to have flexibility and belightweight. Conventional brackets by which the engine is coupled to theframe are constructed of plates with a predetermined uniform thicknessto have desired strength. Since the entirety of the brackets is of apredetermined uniform thickness, weight increases and suitableflexibility is difficult to obtain. If the thickness of the brackets isadjusted to provide suitable flexibility, then desired strength may bedifficult to obtain.

SUMMARY OF THE INVENTION

The present invention addressees the above described conditions, and anobject of the present invention is to provide a vehicle frame structureof a motorcycle that improves assembling efficiency by reducing weldedcomponents. Another object of the present invention is to provide avehicle frame structure of a motorcycle in which a main frame, a pivotframe, and a cross member are firmly coupled to each other. A furtherobject of the present invention is to provide an engine bracket that hassuitable strength, stiffness, and flexibility, and is configured tocouple an engine to a vehicle frame.

According to one aspect of the present invention, there is provided aframe of a motorcycle comprising a head pipe configured to support asteering shaft, a first frame configured to extend from the head pipe,through an area above and rearward of an engine, and to an area rearwardof a vehicle body of the motorcycle, a second frame that is locatedunder the first frame and is configured to extend from the head pipe,through an area forward and downward of the engine, and to an arearearward of the vehicle body, a bracket by which a first component ismounted to the second frame, and a coupling member that is mounted tothe second frame and is configured to couple a second component to thesecond frame, wherein the bracket is integral with the coupling memberto form a unitary piece.

In a frame thus constructed, the number of parts to be separately weldedto the frames decreases, and the assembly process is conductedefficiently while assuring positioning accuracy with which componentsare mounted to the frame.

The first frame may include a main frame that is coupled to the headpipe and configured to extend rearward of the vehicle body. The secondframe may include a down tube that is coupled to the head pipe andconfigured to extend downward from the head pipe and a lower frameconfigured to extend from a lower portion of the down tube, through anarea under the engine, and to an area rearward of the vehicle body. Thecoupling member may include a gusset configured to couple the main frameto an upper portion of the down tube. The bracket may include a radiatormounting bracket by which a radiator is mounted to the down tube. Thegusset may be integral with the radiator mounting bracket to form aunitary piece. Since the gusset is integral with the radiator mountingbracket, it is not necessary to weld these components separately.

The gusset may include a base portion that is disposed behind the upperportion of the down tube and is configured to couple the main frame tothe down tube, and an extending portion configured to extend forward ofthe vehicle body from the base portion to a lateral side of the downtube. The radiator mounting bracket may be integral with the extendingportion to form a unitary piece. Since it is not necessary tomanufacture the gusset and the radiator mounting bracket separately, thenumber of components decreases.

The bracket may include an engine mounting bracket by which the engineis mounted to the second frame. The coupling member may include a guardmounting member by which the second frame is coupled to an engine guardconfigured to cover the engine from below. The engine mounting bracketmay be integral with the guard mounting member to form a unitary piece.Since the engine mounting bracket is integral with the guard mountingmember, it is not necessary to weld these components separately.

The second frame may include a down tube that is coupled to the headpipe and configured to extend downward from the head pipe and a pair ofright and left lower frames configured to extend from a lower portion ofthe down tube, through an area under the engine, and to an area rearwardof the vehicle body. The engine mounting bracket may have a base portionthat is mounted on an upper region at a position on each of the rightand left lower frames and is configured to mount the engine to each oflower frames, and a protruding portion configured to protrude from thebase portion toward a center in rightward and leftward (lateral)direction of the vehicle body. The guard mounting member may be integralwith the protruding portion of the engine mounting bracket to form aunitary piece. In a frame thus constructed, the engine mounting bracketand guard mounting member are made into a unitary piece with a simpleconstruction.

The first frame may include right and left main frames that are coupledto the head pipe and are configured to extend rearward of the vehiclebody, right and left pivot frames that are respectively coupled to rearportions of the main frames and are configured to extend downward fromthe rear portions of the main frames, and a cross member that isconfigured to extend rightward and leftward (laterally) and to coupleupper portions of the right and left pivot frames to each other. Thecross member may be provided with a suspension bracket to which asuspension unit configured to support a rear wheel is mounted, the crossmember being integral with the suspension bracket to form a unitarypiece. The cross member may have cross member connecting portionsrespectively connected to the main frames and the pivot frames.

Since each of the right and left connecting portions of the cross memberis connected to the main frame and to the pivot frame so as to cover thecoupled portion of the main frame and the pivot frame, the main frameand the pivot frame are coupled to each other firmly.

Each of the cross member connecting portions may have a front connectingportion that is configured to extend forward along the main frame and isconnected to the main frame, and a lower connecting portion that isconfigured to extend downward along the pivot frame and is connected tothe pivot frame. In such a construction, the main frame and the pivotframe are coupled to each other more firmly and, further, the crossmember, the main frame, and the pivot frame are coupled to each otherfirmly.

Each of the cross member connecting portions may be connected to anupper region and a side region of the main frame and the pivot frame. Insuch a construction, the main frame and the pivot frame are coupled toeach other more firmly and, further, the cross member, the main frame,and the pivot frame are coupled to each other firmly.

A concave portion may be formed on each of opposite side walls of upperportions of the right and left pivot frames, and each of the crossmember connecting portions is connected to the pivot frame so as tocover the concave portion. In such a construction, a lightweight pivotframe is achieved while ensuring firm coupling between the frames andbetween the frames and the cross member.

One end portion of a rear end portion of the main frame and an upper endportion of the pivot frame may be configured to have a recess in a sideview, and the other end portion is configured to have a protrusion thatconforms in shape to the recess. The recess and the protrusion may becoupled to each other to form a connecting portion of the rear endportion of the main frame and the upper end portion of the pivot frame.Each of the cross member connecting portions of the cross member may beconnected to the connecting portion. In such a construction, the mainframe and the pivot frame are coupled to each other firmly so as not todeviate in the vertical direction, and long weld length is ensured.

The frame may further comprise an engine bracket by which a first frameis coupled to the engine. The engine bracket may be configured to bemanufactured by forging such that a region which is subjected to tensilestress is larger in thickness than a region in the vicinity of theregion which is subjected to the tensile stress, with the first framecoupled to the engine by the engine bracket.

In the engine bracket thus configured, the region which is required tohave strength sufficient to withstand the tensile stress is madethicker, therefore the engine bracket is able to have suitable strength.In addition, the region in the vicinity of the region that is subjectedto the tensile stress is adjusted to have suitable flexibility whileachieving a lightweight engine bracket. Furthermore, a strong andlightweight engine bracket may be manufactured by a forging process.

The engine bracket may include a frame side connecting portion connectedto the first frame and an engine side connecting portion connected tothe engine disposed under the first frame. A front portion of the enginebracket that is located between the frame side connecting portion andthe engine side connecting portion may be formed to have a thicknesslarger than a region located rearward of the front portion. Since thetensile stress is generated in the front portion of the engine bracket,the front portion is made thicker to obtain optimized strength,stiffness, and weight.

The frame side connecting portion may be provided with two firstthreaded hole portions connected to the first frame, the two firstthreaded hole portions may include a front threaded hole portion and arear threaded hole portion located rearward of the front threaded holeportion, and the engine side connecting portion may be provided with asecond threaded hole portion connected to the engine, the first threadedhole portions being made thicker than a region in the vicinity of thefirst threaded hole portions. A rib portion configured to connect thefront threaded hole portion of the two first threaded hole portions tothe second threaded hole portion may be formed on the engine bracket soas to form the front portion of the engine bracket. In such aconstruction, the strength, stiffness, and weight of the engine bracketcan be easily optimized.

According to another aspect of the present invention, there is provideda frame of a motorcycle comprising a head pipe configured to support asteering shaft, right and left main frames respectively configured toextend rearward of a vehicle body of the motorcycle from the head pipe,right and left pivot frames that are respectively coupled to rearportions of the main frames and are configured to extend downward fromthe rear portions of the main frames, and a cross member that isconfigured to extend rightward and leftward (laterally) and to coupleupper portions of the right and left pivot frames to each other. Thecross member may be provided with a suspension bracket by which asuspension unit configured to support a rear wheel is mounted, and thecross member is integral with the suspension bracket to form a unitarypiece. The cross member may have cross member connecting portionsrespectively connected to the main frames and the pivot frames.

Since each of the right and left connecting portions of the cross memberis connected to the main frame and to the pivot frame so as to cover thecoupled portion between the main frame and the pivot frame, the mainframe and the pivot frame are coupled to each other firmly.

Each of the cross member connecting portions may have a front connectingportion that is configured to extend forward along the main frame and isconnected to the main frame and a lower connecting portion that isconfigured to extend downward along the pivot frame and is connected tothe pivot frame. In such a construction, the main frame and the pivotframe are coupled to each other more firmly and, further, the crossmember, the main frame, and the pivot frame are coupled to each otherfirmly.

Each of the cross member connecting portions may be connected to anupper region and a side region of the main frame and the pivot frame.Thereby, the main frame and the pivot frame are coupled to each otherfirmly, and the main frame and the pivot frame are coupled to the crossmember more firmly.

A concave portion may be formed on each of opposite side walls of upperportions of the right and left pivot frames, and each of the crossmember connecting portions may be connected to the pivot frame so as tocover the concave portion. In such a construction, a lightweight pivotframe is achieved while ensuring firm coupling between the frames andbetween the frames and the cross member.

One end portion of a rear end portion of the main frame and an upper endportion of the pivot frame may be configured to have a recess in a sideview, and the other end portion is configured to have a protrusion thatconforms in shape to the recess. The recess and the protrusion may becoupled to each other to form a connecting portion of the rear endportion of the main frame and the upper end portion of the pivot frame.Each of the cross member connecting portions of the cross member may beconnected to the connecting portion. In such a construction, the mainframe and the pivot frame are coupled to each other firmly so as not todeviate in the vertical direction, and long weld length is ensured.

According to another aspect of the invention, an engine bracket by whicha frame of a vehicle is coupled to an engine of the vehicle may beprovided. The engine bracket is typically configured to be manufacturedby forging such that a region which is subjected to tensile stress islarger in thickness than a region in the vicinity of the region which issubjected to the tensile stress, with the frame coupled to the engine bythe engine bracket.

In an engine bracket thus configured, the region which is required tohave strength sufficient to withstand the tensile stress is madethicker, and the engine bracket is able to have suitable strength. Inaddition, the region in the vicinity of the region that is subjected tothe tensile stress is adjusted to have suitable flexibility whileachieving a lightweight engine bracket. Furthermore, a strong andlightweight engine bracket may be manufactured by a forging process.

The engine bracket may include a frame side connecting portion connectedto the upper frame and an engine side connecting portion connected tothe engine disposed under the first frame. A front portion of the enginebracket that is located between the frame side connecting portion andthe engine side connecting portion may be formed to have a thicknesslarger than a region located rearward of the front portion. Since thetensile stress is generated in the front portion of the engine bracket,the front portion is made thicker to obtain optimized strength,stiffness, and weight.

The frame side connecting portion may be provided with two firstthreaded hole portions connected to the first frame, the two firstthreaded hole portions may include a front threaded hole portion and arear threaded hole portion located rearward of the front threaded holeportion, and the engine side connecting portion may be provided with asecond threaded hole portion connected to the engine, the first threadedhole portions being made thicker than a region in the vicinity of thefirst threaded hole portions. A rib portion configured to connect thefront threaded hole portion of the two first threaded hole portions tothe second threaded hole portion may be formed on the engine bracket soas to form the front portion of the engine bracket. In such aconstruction, the strength, stiffness, and weight of the engine bracketcan be easily optimized.

The above and further objects and features of the invention will morefully be apparent from the following detailed description withaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a motocross motorcycle comprising a frameaccording to an embodiment of the present invention;

FIG. 2 is a side view of the frame of the motorcycle of FIG. 1;

FIG. 3 is a side view showing a structure of a gusset according to theembodiment of the present invention;

FIG. 4 is a rear view of the gusset of FIG. 3, as viewed in a directionof arrow IV in FIG. 3;

FIG. 5 is a perspective view showing a structure of a region includingright and left engine mounting brackets mounted to lower frames of FIG.2;

FIG. 6 is a side view of the right engine mounting bracket of FIG. 5;

FIG. 7 is a front view of the engine mounting bracket of FIG. 6 asviewed in a direction of arrow VII in FIG. 6;

FIG. 8 is a plan view of a cross member of FIG. 2;

FIG. 9 is a side view of the cross member of FIG. 8;

FIG. 10 is a rear view of the cross member of FIG. 8;

FIG. 11 is a perspective view showing a connecting configuration of mainframes, pivot frames, and a cross member of FIG. 2;

FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. 11;

FIG. 13 is a side view of a left engine bracket by which a cylinder headof the engine of FIG. 2 is coupled to the pivot frame of FIG. 2, asviewed from outside (left side) in a rightward and leftward (lateral)direction of a vehicle body of the motorcycle;

FIG. 14 is a side view showing a structure of the engine bracket of FIG.13, as viewed from inward in the rightward and leftward (lateral)direction of the vehicle body;

FIG. 15 is a rear view showing a structure of the engine bracket of FIG.13, as viewed from rearward of the vehicle body; and

FIG. 16 is a partial cross-sectional view showing the frame and theengine of FIG. 2, which are partly cut away along line XVI-XVI in FIG.2.

DETAILED DESCRIPTION

Hereinafter, a frame of a motorcycle according to an embodiment of thepresent invention will be described with reference to the drawings. FIG.1 is a side view of a motocross motorcycle 1. FIG. 2 is a side view of aframe 2 of the motorcycle 1 of FIG. 1. The frame 2 of this embodiment istypically made of aluminum alloy, however it will be appreciated thatthe frame may alternatively be made of other suitable materials. In FIG.1, the frame 2 is illustrated by a solid line and the other parts areillustrated by two-dotted lines. Herein, directions are defined from theperspective of a rider (not shown) straddling the motorcycle 1.

Turning now to FIG. 1, the motorcycle 1 comprises a front fork 3extending substantially vertically with a predetermined caster angle. Afront wheel 4 which is a steering wheel is rotatably mounted to a lowerportion of the front fork 3. A lower portion of the steering shaft 6extending substantially vertically is coupled to an upper portion of thefront fork 3. A bar-type steering handle 7 extending rightward andleftward (laterally) is attached at a center region thereof to an upperportion of the steering shaft 6. The frame 2 includes a head pipe 10 anda main frame (first frame) 11 extending slightly downward and rearwardfrom an upper portion of the head pipe 10. The steering shaft 6 isrotatably mounted to the head pipe 10. The front wheel 4 is caused toturn to the right or to the left by the rider's operation of rotatingthe steering handle 7 to the right or to the left.

As shown in FIGS. 1 and 2, the main frame 11 includes a pair of rightand left main frame members 11R and 11L (the left frame member 11L isillustrated in FIGS. 1 and 2, and the right main frame member 11R isillustrated in FIG. 4). A down tube (forming part of a second frame) 12extends downward and slightly rearward from a lower portion of the headpipe 10. A lower frame (forming part of a second frame) 13 extends froma lower portion of the down tube 12. The lower frame 13 includes a pairof right and left lower frame members 13R and 13L (the left lower framemember 13L is illustrated in FIGS. 1 and 2, and the right lower framemember 13R is illustrated in FIG. 5). The lower frame members 13R and13L extend substantially downward with a distance between them thatincreases in a downward direction and then are curved to extendrearward.

A pivot frame (also referred to as a swing arm bracket) 14 is coupled toa rear portion of the lower frame 13 and to a rear portion of the mainframe 11. The pivot frame 14 includes a pair of right and left pivotframe members 14R and 14L. The left pivot frame member 14L is coupled toa rear portion of the left main frame member 11L and to a rear portionof the left lower frame member 13L. The right pivot frame member 14R iscoupled to a rear portion of the right main frame member 11R and to arear portion of the right lower frame member 13R. In FIGS. 1 and 2, onlythe left pivot frame member 14L of the pivot frame 14 is illustrated.

As shown in FIG. 2, a tongue piece 10A for the main frame 11 extendssubstantially rearward from an upper portion of the head pipe 10 andsupports a front portion of the main frame 11 to cover it from above. Atongue piece 10B for the down tube 12 extends substantially downwardfrom a lower portion of the head pipe 10 and supports an upper portionof the down tube 12 to cover it from the front.

As shown in FIG. 2, a pivot hole 14A is formed at a location which isslightly lower than a center in a vertical direction of the left pivotframe member 14L. A swing arm 16 extends substantially forward andrearward and is coupled at a front end portion thereof to be verticallypivotable around a pivot 14B inserted into the pivot hole 14A. As shownin FIG. 1, a rear wheel 5, which is a drive wheel, is rotatably mountedto a rear portion of the swing arm 16.

As shown in FIG. 2, a suspension unit 17 is disposed between an upperportion of the pivot frame 14 and the swing arm 16. The suspension unit17 is pivotally mounted at an upper portion thereof to a cross member 20that is mounted between the left pivot frame 14L member and the rightpivot frame member 14R by a suspension bracket 21. The suspension unit17 is configured to apply a force to bias the swing arm 16 downward.

As shown in FIGS. 1 and 2, a gusset 22 and a support bar 23 are mountedbetween the front portion of the main frame 11 and the rear portion ofthe down tube 12 to increase strength of the frame 2. The gusset 22 isintegral with a radiator mounting bracket 24 to form a unitary piece(see FIG. 2) as described later. A radiator 18 is mounted on theradiator mounting bracket 24 and is positioned in front of the down tube12.

An engine E is mounted in a space S defined by the head pipe 10, themain frame 11, the down tube 12, the lower frame 13, and the pivot frame14. The engine E is a four-cylinder four-cycle engine in thisembodiment. The engine E includes a crankcase 30, a cylinder block 31, acylinder head 32, and a cylinder head cover 33 in this order from below.

The engine E is mounted to the frame 2 by a plurality of engine brackets35, 36, and an engine mounting bracket 37 (see FIG. 2). As shown in FIG.2, the engine bracket 35 is positioned between an engine mountingbracket 14S formed at a lower portion of an upper end of the pivot frame14 and an engine mounting boss 14T formed at a lower portion of a rearportion of the cylinder head 32 of the engine E and is configured tocouple the bracket 14S and the boss 14T to each other. The enginebrackets 35 are provided to correspond to the right and left pivot framemembers 14R and 14L, respectively and are configured to support thecylinder head 32 of the engine E from right and left sides (see FIG.16).

The engine bracket 36 is positioned between an engine mounting bracket13C formed at a rear portion of an upper end of the lower frame 13 andan engine mounting boss 13D formed at a front portion of an upperportion of the crankcase 30 of the engine E and is configured to couplethe bracket 13C and the boss 13D to each other. The engine mountingbracket 37 is positioned between an upper portion at a substantiallycenter in forward and rearward direction of the lower frame 13 and alower portion of the crankcase 30 of the engine E and is configured tocouple the lower frame 13 and the crankcase 30 to each other.

As shown in FIG. 1, an output shaft (not shown) of the engine E iscoupled to the rear wheel 5 through a chain C. A drive force of theengine E is transmitted to the rear wheel 5 through the chain C, therebygenerating a power to move the motorcycle 1. The drive force of theengine E may alternatively be transmitted to the rear wheel 5 through abelt or through a shaft.

As shown in FIG. 1, a fuel tank 26 is disposed above the main frame 11and behind the steering shaft 6. A seat 27 which is straddled by therider is disposed behind the fuel tank 26.

A structure of the gusset 22 and a structure of the engine mountingbracket 37 will now be described. FIG. 3 is a side view showing thestructure of the gusset 22. FIG. 4 is a rear view of the gusset 22 ofFIG. 3, as viewed in a direction of arrow IV in FIG. 3. In FIGS. 3 and4, the main frame 11 (including frame members 11L or 11R) and the downtube 12 are indicated by two-dotted line.

As shown in FIG. 3, the gusset 22 includes an elongated base portion 40configured to extend substantially vertically to couple the main frame11 to the down tube 12, and extending portions 41 configured to extendsubstantially forward (in a direction perpendicular to the direction inwhich the base portion 40 extends) from right and left sides of the baseportion 40. The base portion 40 includes a down tube connecting portion42 configured to extend substantially vertically in the longitudinaldirection of the down tube 12. The down tube connecting portion 42covers a rear surface of the down tube 12. The down tube connectingportion 42 is channel-shaped (substantially U-shaped) such that itshorizontal cross-section that is substantially sectioned in thedirection perpendicular to the longitudinal direction opens forward. Thedown tube connecting portion 42 has a width substantially equal to awidth of an upper portion of the down tube 12. The gusset 22 is coupledto the down tube 12 in such a manner that a region 22A extending along afront peripheral region of each of right and left side walls 42B of thedown tube connecting portion 42 is welded to an outer wall of the downtube 12.

The base portion 40 further includes a main frame connecting portion 43that is located above the down tube connecting portion 42 and isconfigured to be coupled to the main frame 11. The main frame connectingportion 43 includes an inner connecting portion 43A extending in a clawshape from an upper portion of a rear wall 42A (see FIG. 4) of the downtube connecting portion 42, and a triangular lower connecting portion43B extending from an upper portion of each of right and left side walls42B of the down tube connecting portion 42. As shown in FIG. 4, theinner connecting portion 43A has a width slightly larger than a width ofthe down tube connecting portion 42.

As shown in FIGS. 3 and 4, a front portion of each of the right and leftmain frame members 11R and 11L configured to extend rearward with adistance between them that increases in a rearward direction is coupledto the main frame connecting portion 43. The left main frame member 11Lextends rearward and leftward from forward of the gusset 22. An outerwall of the front portion of the main tube (left main frame member 11L)that is closer to a center in the width direction is supported by a leftregion of the inner connecting portion 43A of the main frame connectingportion 43, and an outer wall located thereunder is supported by thelower connecting portion 43B of the main frame connecting portion 43.Under this condition, a region 22B of the gusset 22 extending along aperipheral region of the main frame connecting portion 43 is welded tothe outer wall of the left main frame member 11L so that the gusset 22is coupled to the left main frame member 11L.

The gusset 22 is coupled to the right main frame member 11R in the samemanner. To be specific, the right main frame member 11R extends rearwardand rightward from forward of the gusset 22. An outer wall of a frontportion of the right main frame member 11R that is closer to a center inthe width direction is supported by a right region of the innerconnecting portion 43A of the main frame connecting portion 43, and anouter wall located thereunder is supported by the lower connectingportion 43B of the main frame connecting portion 43. Under thiscondition, a region 22C (see FIG. 4) of the gusset 22 extending alongthe peripheral region of the main frame connecting portion 43 is weldedto the outer wall of the right main frame member 11R so that the gusset22 is coupled to the right main frame member 11R.

A bar mounting portion 44 to which the support bar 23 is mounted isattached at a location slightly lower than the center in thelongitudinal direction of the down tube connecting portion 42 of thegusset 22. The bar mounting portion 44 extends rightward and leftward(laterally) at a rear portion of the down tube connecting portion 42. Avertical cross-section (cross-section sectioned in the directionperpendicular to the longitudinal direction) of the bar mounting portion44 is channel-shaped (substantially U-shaped) to open rearward. Thesupport bar 23 is substantially U-shaped to open rearward as viewed fromabove and a center region 23A of the support bar 23 is fitted to the barmounting portion 44. As shown in FIG. 2, each of right and left endportions 23B extends rearward from the center region 23A and is coupledto a lower face of the rear portion of the corresponding main framemember 11L or 11R. The support bar 23 is coupled to the bar mountingportion 44 and to the main frame 11 in such a manner its peripheralregion is welded to the corresponding region of the bar mounting portion44 and the main frame 11.

As shown in FIG. 3, the extending portion 41 extends (or protrudes)forward from an intermediate position in the longitudinal direction ofeach of the right and left side walls 42B of the down tube connectingportion 42. The extending portion 41 is provided with a radiatormounting bracket 24 having a penetrating hole 24A extending therethroughrightward and leftward (laterally). A bolt (not shown) is inserted intothe penetrating hole 24A to allow the radiator 18 (see FIG. 2) to bemounted to the radiator mounting bracket 24. The gusset 22 of thisembodiment is manufactured by forging or by casting. The radiatormounting bracket 24 is manufactured integrally with the gusset 22 toform a unitary piece. A region 22D of the gusset 22 extending along aperipheral region of the radiator mounting bracket 24 is welded to anouter wall of the down tube 12.

As described above, since the radiator mounting bracket 24 is integralwith the gusset 22 to form a unitary piece, the number of componentsdecreases and welding work becomes less burdensome in contrast to a casewhere the gusset 22 and the radiator mounting bracket 24 are separatelymanufactured and are individually welded to the down tube 12. Inaddition, since the gusset 22 and the radiator mounting bracket 24 aremanufactured integrally by forging or by casting, the radiator mountingbracket 24 is positioned with respect to the gusset 22 with accuracy. Asa result, the radiator 18 is mounted to the radiator mounting bracket 24with higher positioning accuracy.

In this embodiment, since the upper portion of the down tube issandwiched from the front and rear by the down tube tongue piece 10B ofthe head pipe 10 and the gusset 22, an area of an exposed region 12A(see FIG. 3) of the down tube 12 which is between the down tube tonguepiece 10B and the gusset 22 is small. Welding of an independent radiatormounting bracket to the small exposed region 12A described above iscomplicated. The gusset 22 of this embodiment advantageously makes itpossible to omit such a process.

A structure of the engine mounting bracket 37 will be described. Asshown in FIG. 2, the lower frame 13 extends downward from the lower endportion of the down tube 12 and then is curved to extend rearwardsubstantially horizontally. The engine mounting bracket 37 is disposedon a front portion of a horizontal portion 13A of the lower frame 13.

FIG. 5 is a perspective view showing a structure of a region includingthe engine mounting bracket 37 mounted to the lower frame 13. As shownin FIG. 5, the engine mounting bracket 37 includes a left enginemounting bracket 37L and a right engine mounting bracket 37R which aredisposed on the left lower frame member 13L and the right lower framemember 13R, respectively. An engine guard 60 is disposed between theright and left lower frame members 13R and 13L and is configured tocover the engine E from below.

The engine guard 60 is formed of a plate having a plurality of punchholes to reduce weight. The engine guard 60 includes a lower coverportion 61 that is configured to extend forward and rearward along thehorizontal portions 13A of the right and left lower frame members 13Rand 13L and to cover the engine E from below, and a front cover portion62 that is configured to extend upward from a front portion of the lowercover portion 61 and to cover a front portion of a lower portion of theengine E. The engine guard 60 is mounted at a front position of thelower cover portion 61 to the right and left lower frame members 13R and13L by the right and left engine brackets 37R and 37L, respectively.

FIG. 6 is a side view of the right engine mounting bracket 37R of FIG.5. FIG. 7 is a front view of the right engine mounting bracket 37R asviewed in a direction of arrow VII in FIG. 6. As shown in FIG. 6, theengine mounting bracket 37R has a base portion 53 that is of a plateshape with a relatively large wall thickness and is substantiallylozenge-shaped in a side view. The base portion 53 extends verticallywith a normal line oriented rightward and leftward (laterally). The baseportion 53 is provided at an upper region thereof with a penetratinghole 54 extending rightward and leftward (laterally). The engine E (seeFIG. 2) is fastened to the engine mounting bracket 37R by a fastenerbolt (not shown) inserted into the penetrating hole 54.

A protrusion 55 with a large wall thickness extends to the left, (i.e.toward the center in the width direction of the vehicle body) from alower region of the base portion 53 of the engine mounting bracket 37R.The protrusion 55 is manufactured integrally with the base portion 53 byforging or by casting. The protrusion 55 forms a guard mounting member51 to which the engine guard 60 is mounted. As shown in FIGS. 6 and 7,the guard mounting member 51 has a rectangular cross-section withrounded corners in an upper region thereof when sectioned along a plane(vertical plane along the longitudinal direction of the vehicle body)parallel to the base portion 53, and has stiffness sufficient to supportthe engine guard 60. The guard mounting member 51 is provided with apenetrating hole 52 extending substantially vertically in the vicinityof a tip end thereof. The engine guard 60 is mounted to the guardmounting member 51 by a fastener bolt (not shown) inserted into thepenetrating hole 52.

As shown in FIG. 7, a plate-shaped extending portion 56 having asubstantially horizontal face extends in an opposite direction to theprotrusion 55 from a location slightly lower than the center in thevertical direction of the base portion 53 of the engine mounting bracket37R. The extending portion 56 is manufactured integrally with the baseportion 53 to form a unitary piece by forging or by casting. Theextending portion 56 has a lower face conforming in shape to an upperface of a region of the lower frame member 13R at which the extendingportion 56 is connected to the lower frame member 13R.

As shown in FIG. 5, the right engine mounting bracket 37R is disposed onan upper region of the horizontal portion 13A of the right lower framemember 13R. More specifically, the right engine mounting bracket 37R isdisposed on the right lower frame member 13R in such a manner that anouter face (right side face) of a lower portion of the base portion 53extending vertically is in contact with an inner face (left side face)of the right lower frame member 13R and a lower face of the extendingportion 56 is in contact with an upper face of the lower frame member13R. The right engine mounting bracket 37R is coupled to the right lowerframe member 13R in such a manner that a region 50A along a peripheralregion of a lower portion of the base portion 53 and a peripheral regionof the extending portion 56 is welded to the inner face and the upperface of the right lower frame 13R. An upper portion of the base portion53 having the penetrating hole 54 for allowing the engine E to befastened thereto by the fastener bolt protrudes upward from the rightlower frame member 13R and the guard mounting member 51 having thepenetrating hole 52 for allowing the engine guard 60 to be threadedlyfastened thereto protrudes inward in the width direction of the vehiclebody.

The left engine mounting bracket 37L is substantially symmetric to theright engine mounting bracket 37R, and therefore its structure will notbe further described. The left engine mounting bracket 37L is coupled tothe left lower frame member 13L in the same manner that the right enginemounting bracket 37R is coupled to the right lower frame member 13R,which will not be further described, either.

Since the right and left engine mounting brackets 37R and 37L areintegral with the guard mounting members 51 to form a unitary piece, thenumber of components decreases, and welding work becomes less burdensomein contrast to a case where the right and left engine mounting brackets37R and 37L and the guard mounting members 51 are manufacturedseparately and are individually welded to the right and left lower framemembers 13R and 13L, respectively. In addition, since the enginemounting brackets 37R and 37L are manufactured integrally with the guardmounting members 51 by casting or by forging, the guard mounting members51 are positioned with respect to the right and left engine mountingbrackets 37R and 37L with accuracy. As a result, the engine guard 60 ismounted to the engine E with higher positioning accuracy.

Since the guard mounting members 51 integral with the engine mountingbrackets 37L and 37R have rectangular-cross sections and have arelatively large wall thickness, they have sufficient stiffness. Duringtravel of the motocross motorcycle 1, the stiff guard mounting members51 are highly resistant to an impact applied externally to the engineguard 60.

The present invention is applicable to cruising and touring typemotorcycles and road racer motorcycles as well as to the above mentionedmotocross motorcycles. In addition, the present invention is applicableto a frame including a single main frame member, a frame including twodown tubes, or a frame including a single lower frame member as well.

A structure of the cross member 20, and a connecting configuration ofthe main frame 11, the pivot frame 14 and the cross member 20 will bedescribed. FIG. 8 is a plan view of the cross member 20 of FIG. 2. FIG.9 is a side view of the cross member 20 of FIG. 8. FIG. 10 is a rearview of the cross member 20. FIG. 11 is a perspective view showing aconnecting configuration of the main frame 11, the pivot frame 14, andthe cross member 20.

As shown in FIG. 8, the cross member 20 includes a cross portion 70extending rightward and leftward (laterally) and cross member connectingportions 71 provided at both ends of the cross portion 70, and ismanufactured integrally by casting. As indicated by a broken line in theside view of FIG. 9, the cross portion 70 is of a hollow tubular shapeand has a rear side wall 70A at a rear outer peripheral region thereofand an upper side wall 70B at an upper outer peripheral region thereof.The rear side wall 70A forms a substantially vertical wall face with anormal line oriented substantially rearward. The upper side wall 70Bforms a substantially horizontal wall face with a normal line orientedsubstantially upward. The rear side wall 70A and the upper side wall 70Bextend over substantially the entire length in a rightward and leftward(lateral) direction of the cross portion 70. As described later, holes76A are formed on an upper connecting face 76 (see FIG. 9) of the crossmember connecting portion 71 extending downward from each of right andleft end portions of the cross portion 70 and are configured tocommunicate with an inner space of the cross portion 70 to discharge acore of sand that may fill in the inner space during the castingprocess. The cross portion 70 is of a hollow tube shape with asubstantially closed peripheral region as illustrated in FIG. 9, but mayalternatively be of a hollow tube shape with an open lower portion. In afurther alternative, ribs may be suitably provided on the cross portion70 to increase strength.

As shown in FIGS. 8 and 9, a pair of right and left suspension brackets21 protrude rearward from the rear side wall 70A at a center inrightward and leftward (lateral) direction of the cross portion 70. Thesuspension unit 17 (see FIG. 2) is pivotally mounted at an upper portionthereof to the suspension brackets 21. The right and left suspensionbrackets 21 extend in parallel to be spaced a predetermined distancefrom each other. Penetrating holes 21A are formed on rear portions ofthe suspension brackets 21 in such a manner that their center axesconform to each other. Support pins (not shown) are inserted into thepenetrating holes 21A.

As shown in FIGS. 8 and 9, a pair of right and left rail brackets 72protrude upward from the upper side wall 70B. The rail brackets 72 arelocated forward relative to the suspension brackets 21 and at asubstantially center in rightward and leftward (lateral) direction ofthe cross portion 70. Seat rails (not shown) are mounted to the railbrackets 72. The right and left rail brackets 72 are arranged inparallel to be spaced apart from each other. Penetrating holes 72A areformed on upper regions of the rail brackets 72 in such a manner thattheir center axes conform to each other. Support pins (not shown) areinserted into the penetrating holes 72A.

The suspension brackets 21 and the rail brackets 72 are manufacturedintegrally with the cross member 20 by casting. This improves firmconnection between these elements and dimension precision in contrast toa case where the suspension brackets 21 and the rail brackets 72 areseparately manufactured and welded. It shall be appreciated that one ormore of the cross member 20, the suspension brackets 21, and the railbrackets 72 need not be formed by casting (e.g., die casting) but may beformed by, for example, forging or pressing.

As shown in FIG. 10, the cross member connecting portions 71 extenddownward from right and left end portions of the cross portion 70. Whenviewed from the rear, the right and left cross member connectingportions 71 extend downward such that a distance between them graduallyincreases in a downward direction, and a connecting portion of the crossportion 70 to each of the cross member connecting portions 71 iscircular-arc shaped. As shown in FIGS. 8 and 9, an extending portion 74is formed at a lower region of each cross member connecting portion 71so as to extend rearward and downward from a forward and upwardlocation. As shown in FIG. 8, as viewed from above, a region of thecross member 20 extending from an end region of the cross portion 70 toa front region and a rear region of the extending portion 74 has acircular-arc outer shape. As shown in FIG. 9, as viewed from the side, aregion of the cross member 20 extending from an upper region of thecross member connecting portion 71 to a front region and a rear regionof the extending portion 74 has a circular-arc outer shape. Since theconnecting region of these portions of the cross member 20 is of acircular-arc outer shape, the load applied to the cross portion 70 isefficiently transmitted to the extending portion 74 of the cross memberconnecting portion 71.

The extending portion 74 has an inner connecting face 75 extending alongthe longitudinal direction of the extending portion 74 to form asubstantially vertical face and an upper connecting face 76 extendingoutward in the rightward and leftward (lateral) direction of the crossmember 20 from an upper region of the inner connecting face 75. As shownin FIG. 11, the inner connecting face 75 extends along an inner face ofa rear region of the main frame 11 and an inner face of an upper regionof the pivot frame 14 and along the longitudinal direction of the frames11 and 14 at a region surrounding a connecting portion (hereinafterreferred to as a frame connecting portion) 77 of the main frame 11 andthe pivot frame 14. The upper connecting face 76 extends along an upperface of the rear region of the main frame 11 and an upper face of theupper region of the pivot frame 14 and along the longitudinal directionof the frames 11 and 14 at a region surrounding the frame connectingportion 77 of the main frame 11 and the pivot frame 14. As shown in FIG.9, the holes 76A are formed at substantially the center in thelongitudinal direction of the upper connecting face 76 to discharge acore of sand that may fill in the cross portion 70 during casting.

As shown in FIG. 11, in the cross member 20, the extending portion 74 ofthe cross member connecting portion 71 has a front connecting portion71A that extends forward along the main frame 11 and is connected to themain frame 11 and a lower connecting portion 71B that extends downwardalong the pivot frame 14 and is connected to the pivot frame 14.Further, a region between the front connecting portion 71A and the lowerconnecting portion 71B is connected to the frame connecting portion 77of the main frame 11 and the pivot frame 14.

As shown in FIG. 11, an upper end portion 14E of the pivot frame 14 isconfigured to be cut out in substantially U-shape to open forward in aside view. A rear end portion 11E of the main frame 11 is configured toconform in shape to the upper end portion 14E of the pivot frame 14. Inother words, the rear end portion 11E of the main frame 11 is configuredto be cut out to form a substantially trapezoidal shape. The upper endportion 14E of the pivot frame 14 is formed such that a center region inthe vertical direction is cut out in substantially trapezoidal shape toconform to the shape of the rear end portion 11E of the main frame 11,thereby forming upper and lower pointed ends 14F and 14G at upper andlower regions of the upper end portion 14E. The upper end portion 14E ofthe pivot frame 14 has an end face 14H that is located between the upperand lower pointed ends 14F and 14G to extend in a directionsubstantially perpendicular to the longitudinal direction of the pivotframe 14. The main frame 11 and the pivot frame 14 are coupled to eachother in such a manner that the rear end portion 11E of the main frame11 and the upper end portion 14E of the pivot frame 14 are buttedagainst each other, and a butted region is welded. Thus, the main frame11 and the pivot frame 14 are coupled to each other with a long weldlength, thereby improving coupling strength of the frames 11 and 14.Concave portions 14C are formed on inner regions of upper portions ofthe pivot frames 14, i.e., opposite side walls of the right and leftpivot frame members 14R and 14L. A number of ribs 14D are providedwithin the concave portions 14.

The above mentioned cross member 20 is mounted between the right andleft frame connecting portions 77 of the main frames 11 and the pivotframes 14. As shown in FIG. 11, the cross member 20 is mounted fromabove between the right and left frame connecting portions 77 such thatthe longitudinal direction of the cross portion 70 corresponds with therightward and leftward (lateral) direction. The right and left innerconnecting faces 75 of the cross member connecting portions 71 areconfigured to contact the right and left connecting portions 77 frominward in the rightward and leftward (lateral) direction of the vehiclebody. The upper connecting faces 76 of the cross member connectingportions 71 are configured to contact the frame connecting portions 77from above.

The inner connecting face 75 and the upper connecting face 76 of eachcross member connecting portion 71 cover inner regions and upper regionsof each frame connecting portion 77 between the frames 11 and 14, therear end portion 11E of each main frame 11, and the upper end portion14E of each pivot frame 14. Under this condition, an outer peripheralregion of the inner connecting face 75 of the cross member connectingportion 71 and an outer peripheral region of the upper connectingportion 76 of the cross member connecting portion 71 are welded to theouter wall of the main frame 11, and the outer wall of the pivot frame14 so that the cross member 20, the main frame 11, and the pivot frame14 are firmly coupled to each other.

As shown in FIG. 12, which is a cross-sectional view taken along lineXII-XII in FIG. 11, the concave portion 14C formed on the upper regionof the pivot frame 14 and the cross member connecting portion 71 of thecross member 20 that covers the concave portion 14C form a hollowstructure having an inner space 79, which is able to ensure strength.Therefore, the ribs 14D may be omitted in the interior of the concaveportion 14C covered with the cross member connecting portion 71, asillustrated in this embodiment.

As shown in FIG. 11, a recess 78 is formed in a region of the main frame11 and the pivot frame 14 which is configured to contact the crossmember connecting portion 71 of the cross member 20. The cross member 20is mounted between the main frame 11 and the pivot frame 14 in such amanner that the cross member connecting portion 71 is fitted into therecess 78. Thus, the cross member 20 is easily positioned with respectto the main frame 11 and the pivot frame 14.

In accordance with the frame 2 constructed above, the cross member 20,the main frames 11, and the pivot frames 14 are firmly coupled to eachother, and the load applied to the cross member 20 through thesuspension brackets 21 is efficiently transmitted and dispersed from theextending portions 74 of the cross member connecting portions 71 of thecross member 20 to the main frames 11 and the pivot frames 14.

The frame of the present invention is applicable to cruising and touringtype motorcycles and road racer motorcycle as well as to the abovementioned motocross motorcycles.

A structure of the engine bracket 35 will be described. FIG. 13 is aside view showing the left engine bracket 35L by which the pivot frame14 is coupled to the cylinder head 32 of the engine E, as viewed fromoutward (the left side) in the rightward and leftward (lateral)direction of the motorcycle 1. FIG. 14 is a side view showing astructure of the engine bracket 35L as viewed from inward in therightward and leftward (lateral) direction of the vehicle body of themotorcycle 1. FIG. 15 is a rear view showing a structure of the enginebracket 35L as viewed from rearward of the vehicle body. The right andleft brackets 35R and 35L are manufactured from aluminum alloy byforging, and are shaped to have suitable strength, stiffness, and weightas described later.

As shown in FIG. 13, the left engine bracket 35L has a base plate 90that is inverted-triangle shaped in a side view and has a predeterminedthickness d1 (see FIG. 15). Front and rear hole portions 91 and 92 areformed on an upper region of the base plate 90. The bolt hole portions91 and 92 form frame side connecting portions 100 which are configuredto be fastened to the engine mounting bracket 14S (see FIG. 2) of theleft pivot frame 14L. As shown in FIG. 14, the bolt hole portions 91 and92 are of a circle shape. Bolt holes 91 a and 92 a are formed at thebolt hole portions 91 and 92 to extend therethrough in a thicknessdirection of the base plate 90. The bolt holes 91 a and 92 a haveelongate circle (substantially oval) cross-sections.

As shown in FIG. 15, the bolt hole portion 92 has a thickness d2slightly larger than the thickness d1 of the base plate 90 and protrudesinward (rightward) of the vehicle body from an inner face 90 c of thebase plate 90. An outer face 92 b of the bolt hole portion 92 is flushwith an outer face 90 b of the base plate 90, and an inner face 92 c ofthe bolt hole portion 92 is located inward of the vehicle body relativeto the inner face 90 c of the base plate 90. Although not shown in FIG.15, the bolt hole portion 91 has the thickness d2 and protrudes inwardof the vehicle body from the inner face 90 c of the base plate 90 as inthe bolt hole portion 92. The outer face 91 b of the bolt hole portion91 in FIG. 13 is flush with the outer face 90 b of the base plate 90,and the inner face 91 c of the bolt hole portion 91 in FIG. 14 islocated inward of the vehicle body relative to the inner face 90 c ofthe base plate 90.

As shown in FIGS. 13 and 14, a bolt hole portion 93 is formed on a lowerregion of the base plate 90. The bolt hole portion 93 forms an engineside connecting portion 101 fastened to the engine mounting boss 14T(see FIG. 2) of the cylinder head 32 of the engine E by a fastener bolt.A bolt hole 93 a is formed on the bolt hole portion 93 to extendtherethrough in the thickness direction of the base plate 90. As shownin FIG. 15, the bolt hole portion 93 has a thickness d3 larger than thethickness d1 of the base plate 90 and protrudes inward (rightward) ofthe vehicle body from the inner face 90 c of the base plate 90 as in theabove mentioned bolt holes 91 and 92. To be specific, an outer face 93 bof the bolt hole portion 93 is flush with an outer face 90 b of the baseplate 90 and an inner face 93 c of the bolt hole 93 is located inward ofthe vehicle body relative to the inner face 90 c of the plate. In thisembodiment, the thickness d3 of the lower bolt hole portion 93 connectedto the cylinder head 32 of the engine E is set larger than the thicknessd2 of the upper bolt hole portions 91 and 92 which are connected to thepivot frame 14.

As shown in FIG. 14, a rib portion 94 is formed on the front side of thebase plate 90 so as to protrude from the inner surface 90 c of the baseplate 90. The rib portion 94 has a predetermined thickness d4 (see FIG.15) larger than the thickness d1 of the base plate 90. The rib portion94 has a substantially constant width w1 and is configured to couple thefront bolt hole portion 91 of the upper bolt hole portions 91 and 92 tothe lower bolt hole portion 93. In this embodiment, the thickness d4 ofthe bolt hole portion 94 is equal to the thickness d2 of the upper bolthole portion 91 (see FIG. 15). The thickness d4 and the width w1 of therib portion 94 are suitably adjusted so that the engine bracket 35L hasdesired strength and stiffness.

As shown in FIG. 15, as viewed from the rear, the left engine bracket35L is structured such that a middle portion of the base plate 90 isangled at approximately 45 degrees, and the upper portion and lowerportion extend in parallel with each other. As a result, the location ofan upper portion is offset outward of the vehicle body relative to alower portion by a distance d5. The right engine bracket 35R (see FIG.16) is symmetric to the left engine bracket 35L with respect to thecenter in the rightward and leftward (lateral) direction of the vehiclebody, and therefore will not be further described.

As shown in FIG. 2 and FIG. 16, which is a partial cross-sectional viewtaken along line XVI-XVI in FIG. 2, the engine bracket 35R (or 35L) ismounted between the pivot frame member 14R (or 14L) and the cylinderhead 32 and is configured to couple the pivot frame member 14R (or 14L)and the cylinder head 32 to each other First, the engine bracket 35L isdisposed in such a manner that two bolt holes 14U (only rear bolt hole14U is illustrated in FIG. 16) formed on the engine mounting bracket 14Sof the left pivot frame member 14L are coaxial with the bolt holes 91 aand 92 a (only rear bolt hole 92 a is illustrated in FIG. 16) of theupper bolt hole portions 91 and 92 of the left engine bracket 35L,respectively. In this case, the base plate 90 is disposed in such amanner that the outer surface 90 b is oriented outward of the vehiclebody and the rib portion 94 (see FIG. 14) is oriented forward.

The bolts 95 are threaded into the bolt holes 14U and 91 a and the boltholes 14U and 92 a to fasten the engine bracket 35L to the pivot framemember 14L. The bolts 95 are not fastened tightly so that the enginebracket 35L is coupled to the engine mounting bracket 14S of the pivotframe member 14L with some predetermined amount of play within theelongate bolt holes 91 a and 92 a of the engine bracket 35L.

The engine E is incorporated into the frame 2. The engine E is mountedon the frame 2 by the engine bracket 36 and the engine mounting bracket37 (see FIG. 2). Under this condition, the left engine mounting boss 14Tprovided on the cylinder head 32 of the engine E is located forward anddownward relative to the engine mounting bracket 14S of the pivot framemember 14L (see FIG. 2). The engine bracket 35L is disposed with respectto the engine such that the bolt hole 14V formed on the engine mountingboss 14T of the cylinder head 32 is coaxial with the bolt hole 93 a ofthe lower bolt hole portion 93 of the engine bracket 35L. Since theengine bracket 35L and the pivot frame member 14L are coupled to eachother with predetermined amount of play as described above, the boltholes 14V and 93 a are aligned coaxially regardless of some deviationbetween the engine E and the pivot frame 14 when the engine E isincorporated into the frame 2.

Under this condition, the bolts 95 are securely threaded into the boltholes 14V and 93 a so that the engine bracket 35L is fastened to theengine E. In addition, the bolts 95 are surely threaded into the boltholes 14U of the pivot frame member 14L so that the engine bracket 35Lis fastened to the pivot frame member 14L.

The right pivot frame member 14R is coupled to the right engine mountingboss 14T of the cylinder head 32 of the engine E by the engine bracket35R which is symmetric in shape to the left bracket 35L in the samemanner that the left pivot frame member 14L is coupled to the left boss14T of the cylinder head 32. In the right engine bracket 35R of FIG. 16,the same reference numerals as those of the left engine bracket 35Ldenote the same or corresponding parts, which will not be furtherdescribed.

The engine bracket 35 (35L and 35R) by which the pivot frame 14(including members 14L and 14R) is coupled to the engine E extendsdownward and forward from the bolt hole portions 91 and 92 connected tothe engine mounting bracket 14S of the pivot frame 14 to the bolt holeportion 93 connected to the engine mounting boss 14T of the cylinderhead 32 of the engine E. Under this condition, in the engine bracket35L, the rib portion 94 is subjected to tensile stress.

Since the rib portion 94 which is subjected to the tensile stress hasthe relatively large thickness d4, the engine bracket 35L of thisembodiment enables the engine E to be mounted on the pivot frame 14 withsuitable strength. In addition, since a region of the base plate 90which is located rearward of the rib portion 94 has the thickness d1smaller than the thickness d4 of the rib portion 94, a lightweightengine bracket 35L is achieved. Furthermore, since the rib portion 94has the suitable width w1, the engine bracket 35L is able to havesuitable strength and stiffness. As should be appreciated, the enginebracket 35L of the present invention is manufactured in such a mannerthat the thickness d1 of the base plate 90 and the thickness d4 and thewidth w1 of the base portion 94 are suitably adjusted. As a result,strength, stiffness, and weight of the engine bracket 35L are optimizedaccording to, for example, the weight of the engine E.

While in this embodiment the frame side connecting portion 100 of theengine bracket 35L is coupled to the pivot frame 14, it mayalternatively be coupled to the main frame 11. Furthermore, the engineside connecting portion 101 may be coupled to the crankcase 30 insteadof the cylinder head 32.

The engine bracket 35L may be manufactured from materials other thanaluminum alloy and by methods other than the forging, for example, bycasting, cutting, or die casting. The shape of the bolt holes 91 a and92 a (see FIG. 14) is not intended to be limited to the elongate circlebut may be a perfect-circle shape or other suitable shape so long as theengine bracket 35L is coupled to the engine mounting bracket 40 of thepivot frame 14L with suitable play.

The engine bracket of the present invention may be employed to coupleframes to engines of cruising and touring type motorcycles and roadracer motorcycles as well as to motocross motorcycles, and may also beapplied to four-wheeled all terrain vehicles, etc. The above mentionedembodiments are merely exemplary and may be suitably changed within thescope of the present invention.

As this invention may be embodied in several forms without departingfrom the spirit of essential characteristics thereof, the presentembodiments are therefore illustrative and not restrictive, since thescope of the invention is defined by the appended claims rather than bythe description preceding them, and all changes that fall within metesand bounds of the claims, or equivalence of such metes and boundsthereof, are therefore intended to be embraced by the claims.

1. A frame of a motorcycle comprising: a head pipe configured to supporta steering shaft; a first frame configured to extend from the head pipe,through an area above and rearward of an engine, and to an area rearwardof a vehicle body of the motorcycle; a second frame that is locatedunder the first frame and configured to extend from the head pipe,through an area forward and downward of the engine, and to an arearearward of the vehicle body; a bracket by which a first component ismounted to the second frame; and a coupling member that is mounted tothe second frame and is configured to couple a second component to thesecond frame; wherein the coupling member has the bracket; wherein thefirst frame includes right and left main frame members that are coupledto the head pipe and are configured to extend rearward of the vehiclebody, right and left pivot frame members that are respectively coupledto rear portions of the main frame members and are configured to extenddownward from the rear portions of the main frame members, and a crossmember that is configured to extend laterally and to couple upperportions of the right and left pivot frame members to each other;wherein the cross member is provided with a suspension bracket to whicha suspension unit configured to support a rear wheel is mounted; andwherein the cross member has cross member connecting portions eachhaving a front connecting portion connected to a respective one of theright and left main frame members and a lower connecting portionconnected to a respective one of the right and left pivot frame members.2. The frame of a motorcycle according to claim 1, wherein the frontconnecting portion is configured to extend forward from a connectingportion where a respective one of the left and right main frame membersis connected to a respective one of the left and right pivot framemembers and is connected to the respective one of the left and rightmain frame members, and a lower connecting portion is configured toextend downward from a connecting portion where a respective one of theleft and right main frame members is connected to a respective one ofthe left and right pivot frame members and is connected to therespective one of the left and right pivot frame members.
 3. The frameof a motorcycle according to claim 2, wherein each of the cross memberconnecting portions is connected to an upper surface region and asurface region at an inner side in a vehicle width direction in aconnecting portion of a respective one of the left and right main framemembers and a respective one of the left and right pivot frame members.4. The frame of a motorcycle according to claim 3, wherein a concaveportion is formed on each of opposite side walls of upper portions ofthe right and left pivot frame members, and each of the cross memberconnecting portions is connected to a respective one of the pivot framemembers so as to cover the corresponding concave portion.
 5. The frameof a motorcycle according to claim 1, wherein one end portion of a rearend portion of each main frame member and an upper end portion of eachpivot frame member is configured to have a recess in a side view, andthe other end portion is configured to have a protrusion that conformsin shape to the recess; wherein the recess and the protrusion of eachcorresponding main frame member and pivot member are coupled to eachother to form a connecting portion of the rear end portion of the mainframe member and the upper end portion of the corresponding pivot framemember; and wherein each of the cross member connecting portions of thecross member is connected to the connecting portion.
 6. A frame of amotorcycle comprising: a head pipe configured to support a steeringshaft; right and left main frame members respectively configured toextend rearward of a vehicle body of the motorcycle from the head pipe;right and left pivot frame members that are respectively coupled to rearportions of the main frame members and are configured to extend downwardfrom the rear portions of the main frame members; and a cross memberthat is configured to extend laterally and to couple upper portions ofthe right and left pivot frame members to each other; wherein the crossmember is provided with a suspension bracket by which a suspension unitconfigured to support a rear wheel is mounted, the cross member beingintegral with the suspension bracket to form a unitary piece; andwherein the cross member has cross member connecting portionsrespectively connected to the main frame members and the pivot framemembers.
 7. The frame of a motorcycle according to claim 6, wherein eachof the cross member connecting portions has a front connecting portionthat is configured to extend forward along a respective one of the rightand left main frame members and is connected to the respective one ofthe right and left main frame members and a lower connecting portionthat is configured to extend downward along a respective one of theright and left pivot frame members and is connected to the respectiveone of the right and left pivot frame members.
 8. The frame of amotorcycle according to claim 7, wherein each of the cross memberconnecting portions is connected to an upper region and a side region ofa respective one of the left and right main frame members and arespective one of the left and right pivot frame members.
 9. The frameof a motorcycle according to claim 8, wherein a concave portion isformed on each of opposite side walls of upper portions of the right andleft pivot frame members, and each of the cross member connectingportions is connected to a respective one of the pivot frame members soas to cover the corresponding concave portion.
 10. The frame of amotorcycle according to claim 6, wherein one end portion of a rear endportion of each main frame member and an upper end portion of acorresponding pivot frame member is configured to have a recess in aside view, and the other end portion is configured to have a protrusionthat conforms in shape to the recess; wherein the recess and theprotrusion are coupled to each other to form a connecting portion of therear end portion of the main frame member and the upper end portion ofthe corresponding pivot frame member; and wherein each of the crossmember connecting portions of the cross member is connected to arespective connecting portion.